Headlights for a vehicle can produce high beams and low beams interchangeably. The high beams cast high-intensity light over a greater distance, and the low beams illuminate a closer area with a prescribed light intensity. The high beams can provide better visibility, but they may produce glare that affects drivers of vehicles ahead such as preceding or oncoming vehicles.
In order to prevent the glare, some vehicle headlights are provided with the ADB function. The vehicle headlights having the ADB function are configured such that, upon high beam illumination, a position of a vehicle ahead is identified, and in accordance with dimensions and the position of the vehicle, a “shadow (cut-off)” for suppressing the glare to the vehicle ahead is produced in the illumination area, thereby reducing the glare toward a driver of the vehicle ahead. The cut-off is produced by placing a mask (shade) that has dimensions and a position corresponding to those of the vehicle ahead on an image forming device (projector).
In this scheme, by using a mask that can change its shape, the dimensions and the position of the cut-off can be controlled in accordance with a movement of the vehicle ahead (see Patent Document 1 and Patent Document 2, for example). Also, in a scheme to provide the ADB function (ADB system), lights from tail lamps, headlights, or the like of a vehicle ahead are detected from an image of a preceding area captured by a recognition camera provided in a car interior room, and a position of the vehicle is thereby identified (see Patent Document 3, for example).